<template>
	<view>
		<view class="scroll-view-container">
		  <!-- 左侧的滑动区域 -->
      <scroll-view class="left-scroll-view" scroll-y="true" :style="{height: wh + 'px'}">
        <block v-for="(item, i) in cateList" :key="i">
          <view :class="['left-scroll-view-item', i === active ? 'active' : '']" @click="activeChanged(i)">{{item.cat_name}}</view>
        </block>
      </scroll-view>
      <!-- 右侧的滑动区域 -->
      <scroll-view  class="right-scroll-view" scroll-y="true" :style="{height: wh + 'px'}" :scroll-top="scrollTop">
        <view class="cate-lv2" v-for="(item2, i2) in cateLevel2" :key="i2">
            <view class="cate-lv2-title">/ {{item2.cat_name}} /</view>
            <!-- 动态渲染三级分类的列表数据 -->
            <view class="cate-lv3-list">
              <!-- 三级分类 Item 项 -->
              <view class="cate-lv3-item" v-for="(item3, i3) in item2.children" :key="i3" @click="gotoGoodsList(item3)">
                <!-- 图片 -->
                <image :src="item3.cat_icon"></image>
                <!-- 文本 -->
                <text>{{item3.cat_name}}</text>
              </view>
            </view>
          </view>
      </scroll-view>
		</view>
	</view>
</template>

<script>
	export default {
		data() {
			return {
				//当前设备可用高度
        wh: 0,
        //分类数据列表
        cateList: [],
        //默认第一项被选中
        active: 0,
        //二级分类列表
        cateLevel2: [],
        //滚动条距离顶部的距离
        scrollTop: 0
			}
		},
    onLoad() {
      const sysInfo = uni.getSystemInfoSync()
      this.wh = sysInfo.windowHeight
      //调用获取分类列表数据的方法
      this.getCateList()
    },
		methods: {
			async getCateList() {
			    // 发起请求
			    const { data: res } = await uni.$http.get('/api/public/v1/categories')
			    // 判断是否获取失败
			    if (res.meta.status !== 200) return uni.$showMsg()
			    // 转存数据
			    this.cateList = res.message
          //为二级分类赋值
          this.cateLevel2 = res.message[0].children
			 },
       activeChanged(i) {
         this.active = i
         //为二级分类列表重新赋值
         this.cateLevel2 = this.cateList[i].children
         
         // 让 scrollTop 的值在 0 与 1 之间切换
           this.scrollTop = this.scrollTop === 0 ? 1 : 0
       },
       gotoGoodsList(item3) {
         uni.navigateTo({
           url: '/subpkg/goods_list/goods_list?cid=' + item3.cat_id
         })
       }
		}
	}
</script>

<style lang="scss">
.scroll-view-container {
  display: flex;
  
  .left-scroll-view {
    width: 120px;
    
    .left-scroll-view-item {
          line-height: 60px;
          background-color: #f7f7f7;
          text-align: center;
          font-size: 12px;
    
          // 激活项的样式
          &.active {
            background-color: #ffffff;
            position: relative;
    
            // 渲染激活项左侧的红色指示边线
            &::before {
              content: ' ';
              display: block;
              width: 3px;
              height: 30px;
              background-color: #c00000;
              position: absolute;
              left: 0;
              top: 50%;
              transform: translateY(-50%);
            }
          }
        }
  }
  
  .cate-lv2-title {
    font-size: 12px;
    font-weight: bold;
    text-align: center;
    padding: 15px 0
  }
  
  .cate-lv3-list {
  display: flex;
  flex-wrap: wrap;

  .cate-lv3-item {
    width: 33.33%;
    margin-bottom: 10px;
    display: flex;
    flex-direction: column;
    align-items: center;

    image {
      width: 60px;
      height: 60px;
    }

    text {
      font-size: 12px;
    }
  }
}
}
</style>
